[chiefalchemist]

"Violence is absolutely part of human nature. Serial killers are probably pathological but mass murder is definitely within normal human behaviour. The Mongols were less especially brutal than especially organised, ditto for the Nazis at a later date.

Kill everybody and take their land is more or less what happened to both the Neanderthals and the first H. Sapiens in Europe. Kill all the men is practically a humanitarian innovation."

That's the crux of my point. My sense is there's a perception that humans are "highly advanced" and that (e.g.) people with violent tendencies are highly "abnormal" and should - in extreme cases - be put to death.

The irony being their genes are what saved the species in previous generations. But today those genes are not advantageous.